Pelagic dispersal of Norway lobster Nephrops norvegicus larvae examined using an advection-diffusion-mortality model

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Abstract
Norway lobster Nephrops norvegicus (L.) larvae are hatched into the water column from areas of fine mud and spend about 50 d in the plankton before resettling onto mud as juveniles. Whilst in the pelagic environment, however, advection and horizontal turbulent diffusion spread larvae away from the mud region and thus potentially could limit recruitment. A simple advection-diffusion-mortality model has been used to examine the likely losses of larvae from an N. norvegicus system due to pelagic dispersal. Turbuent diffusion alone causes insufficient loss to affect recruitment on mud patches larger than 20 .times. 20 km for reasonable estimates of eddy diffusivity. Low levels of mean advection (0.04 to 0.05 m s-1), however, severely limit settlement even on very large mud areas (100 .times. 100 km). Distributions of larvae released from a mud region in the western Irish Sea consistently show them to be spread southward away from the mud patch although it remains unclear whether advection in the region is sufficiently large for these losses to influence recruitment.